How to draw a picture on the theme of a goldfish. How to draw a goldfish with a pencil? Step by step instructions

Any aluminum spoon - tea or table - is suitable for this experiment. It must be thoroughly washed and degreased; you know how to do this from experiments with anodizing aluminum. The spoon will be the first part of the future rectifier, and the second one for now will be an empty tin can, about the height of a spoon, at least not much lower.

Tin can wash with soap or washing powder, rinse and fill with a solution for anodizing aluminum: per 100 ml of water - 20 ml of sulfuric acid (carefully!). The acid can be replaced with ammonium carbonate (NH 4) 2 CO 3 (10 g) or, as a last resort, baking soda, dissolving it in water until saturated. The water must be distilled, but clean rainwater is also suitable.

Before lowering the spoon into the jar, figure out where the solution will reach on the spoon. At the boundary between the solution and air, aluminum will rapidly dissolve, and the spoon will soon fall apart into two parts. To prevent this from happening, cover the area near the border with a layer of varnish or waterproof glue.

Now hang the spoon in the jar so that it does not touch the walls; You can probably easily come up with a suspension device yourself. Place a tile or any other non-conductive stand under the jar. This time we will not use batteries or an accumulator, but alternating current from the mains, and, naturally, we need to completely protect ourselves. For the same reason, insulate all bare ends of the wires very carefully, and do not touch either the spoon or the jar during the experiment. It is best if you cover them with an upside down plywood box or plastic bucket before turning on the current.

The electrical circuit is simple: connect a lamp with a power of about 40–60 W, a switch, a spoon and a jar in series; If you have an ammeter, you can connect that too. When the circuit is assembled and the insulation reliability is checked, turn on the current.

First, as you might expect, the lamp will light up, because the solution in the jar is electrically conductive. But after about half an hour, it will begin to shine noticeably weaker, and then go out completely. The spoon became a straightener. It passes current in only one direction - from the jar to the spoon.

It would be easy to verify this if you had an oscilloscope: on its screen at the beginning of the experiment a sinusoid would glow, and at the end its lower branch would disappear: a so-called pulse current flows in the circuit. An oscilloscope would help to immediately determine where the positive pole of the rectifier is and where the negative pole is (this is very important if you are going to conduct electrochemical experiments with a homemade rectifier). But you can do without instruments: the polarity of the rectifier can be easily established using a strip of filter paper moistened with a weak solution of table salt with the addition of a phenolphthalein indicator.

Turn off the current, press the sheet of paper against the spoon and the jar and secure it, for example, with plastic clothespins. Turn on the current and a few minutes later the filter paper will turn red at one of the poles. This pole is negative. During the electrolysis of water (salt is needed only to increase electrical conductivity), hydrogen is released at the negative electrode (cathode), and OH ions remain in excess. These ions determine the alkaline properties, which is why the indicator paper turns red.

The same test with wet indicator paper with salt and phenolphthalein can be carried out if you have reversed the poles of the battery or battery. Since the voltage here is low, a strip of paper can simply be pressed with your hands to both poles of the current source.

But why did the aluminum spoon become a straightener? After turning on the current, a film of aluminum oxide grows on it, as when anodizing aluminum. And this film is a semiconductor: it passes current only in one direction. This property is often used in technology.

Using a homemade rectifier, you can perform some electrochemical experiments, which are described in this book. But according to the experimental conditions, turn on the rectifier through a step-down transformer. The voltage should in no case exceed 40 V. And the current that can be drawn from an aluminum spoon can reach several tens of amperes.

But is it necessary to take a spoon and a tin can for the straightener? Of course no. Instead of a spoon, you can take an aluminum electrode of any shape, instead of a jar - an iron, lead or graphite electrode and immerse them in a glass vessel into which an electrolyte solution is poured. Moreover, this is what we advise you to do if you decide to use a homemade straightener in practice. But if you are going to demonstrate how aluminum oxide rectifies alternating current, then a spoon and a jar look much more impressive...

For this experiment, it is more convenient to take a table lamp. Disconnect one of its wires from the plug and extend it, not forgetting about good insulation.

Take a small narrow glass tube with thin walls (the easiest way is to use glass pens with drawn ends). Insert electrodes into the tube from both ends - wires with a diameter of about 1 mm; secure them in the tube with insulating tape. The electrodes should not touch, the distance between them is 1–2 mm.

Attach the extended wire from the lamp to one of the electrodes, and connect the other electrode with a wire to the free socket of the plug and insulate it. You will end up with a circuit that is open in one area - between the electrodes. Secure the glass tube in a horizontal position. This is quite easy to do if the wires are rigid, with plastic insulation: clamp the wire and the tube will hold on to it. Preparations for the experiment are completed, you can plug in the plug. The lamp, of course, will not light.

Bring a lit match to the tube into which the electrodes are inserted. If the tube is not made of refractory glass, then the glass will soften and the tube will sag a little. And the lamp will immediately light up, despite the fact that the circuit still remains open. The fact is that the salts that make up the glass become ionized when heated, and the glass becomes a conductor.

If the experiment does not work because the tube is wide, then take a candle or alcohol lamp instead of a match. Lighting a lamp with a candle is also a spectacular experience.

You can also light it with molten saltpeter. Secure a test tube vertically with a little potassium or sodium nitrate (potassium or sodium nitrate) sprinkled on the bottom and lower two copper wires into it. To prevent the copper electrodes from touching, pass them through the plug. Connect the lamp to the electrodes in the same way as in the previous experiment. When you turn on the current, the lamp naturally will not light up: solid nitrate does not conduct current.

Heat the saltpeter until it melts using dry fuel tablets - the lamp will flash. The ions that made up the crystal lattice of the salt become mobile, and the chain closes. The lamp will burn even after you remove the flame: the nitrate melt has a high electrical resistance, and the heat that is released during the passage of current maintains the nitrate in a molten state.

In a similar way, you can conduct an experiment not with a melt, but with a solution, for example, table salt. In this case, it is better to take graphite electrodes. First, simply immerse them in a jar of water, and then add salt in small portions, and the lamp will glow brighter.

By the way, this method is convenient for checking the electrical conductivity of solutions. Check, for example, how solutions of soda, sugar and acetic acid of different concentrations conduct current.

And one more, not quite ordinary experience with light bulb, but not from a big one, but from a flashlight. Strengthen it in a strip of tin bent at a right angle and insert the strip into a small beaker so that the glass bulb of the light bulb is inside the beaker and faces its bottom. Connect the light bulb to the battery: connect the protrusion on the base, its outermost section with the negative pole, and a strip of tin with the positive one. Please note: you cannot solder the conductors, because the solder may melt during the experiment. You need to come up with a mechanical contact or use a socket from an old flashlight.

Before starting the experiment, remove the lamp from the glass and pour sodium nitrate into it (potassium nitrate is not suitable in this case; why will become clear later). Place the glass on an asbestos mesh or metal plate and heat it over the flame of a gas burner or alcohol lamp; dry alcohol is not very convenient, since it is difficult to regulate the temperature of the melt. Nitrate melts at 309 °C, and at 390 °C it already decomposes; This is the range where you will have to maintain the temperature. To do this, change either the size of the flame or the distance to the glass. Make sure that the melt does not solidify, even from the surface.

Carefully lower the light bulb into the molten saltpeter. Most of the glass container should be immersed in the melt, but make sure that top part the base to which the conductor is soldered does not come into contact with the saltpeter - a short circuit will occur. Keep the lit light bulb in the saltpeter for about an hour, then turn off the current, turn off the burner and carefully remove the light bulb. When it cools down, rinse it with water and you will see that the inside of the light bulb is covered with a mirror layer!

We have already said that when heated, charged particles in glass become mobile (which is why the lamp was lit when the tube was heated with a match). The main characters are sodium ions: already at temperatures above 300 °C they become quite mobile. The glass itself remains completely solid.

When you immersed the switched-on light bulb in the molten saltpeter, the glass from which the can was made found itself in an electric field: the spiral is the negative pole, the melt that comes into contact with the strip of tin is positive. Mobile sodium ions began to move in the glass towards the cathode, i.e. towards the spiral. In other words, they moved towards the inner wall of the balloon.

So, the mirror coating from the inside is sodium? Yes. But how did the ions turn into metal?

Hot metals (including those from which the spiral is made) emit electrons. From the spiral they fell on the inner surface of the glass and combined there with sodium ions. This is how metallic sodium was formed.

But why is potassium nitrate not suitable for the experiment? After all, nitrate does not seem to be involved in the process... No, it is. When the sodium ion became a neutral atom, a negatively charged ionic hole was left in the glass. This is where sodium nitrate is needed: from its melt, under the influence of an electric field, sodium ions penetrate into the glass and fill the holes. And potassium ions are approximately one and a half times larger than sodium ions, they will not be able to enter the glass. In potassium nitrate the lamp will simply crack.

This unusual electrolysis through glass is sometimes used in practice to obtain a layer of very pure sodium, or, more strictly, spectrally pure.

Imagine what happened: you started an electrochemical experiment, assembled a circuit - and the battery suddenly died, and there is no spare battery. What should I do? But that's not so bad. It’s much worse when a flashlight goes out on a dark evening, especially in the forest. And what a shame if the batteries of a transistor radio fail just at the minute when your favorite song is broadcast on the radio, or during a broadcast football match. But what can you do about it...

In the meantime, something can be done. If you don’t have a spare battery, don’t rush to throw away the old one, but try to “revive” it.

Many modern batteries - Krona, Mars, Saturn, KBS and others - consist of elements of the manganese-zinc system. During operation, the negative electrode of these batteries - the zinc cup - gradually, but very slowly, dissolves, and the positive electrode - manganese dioxide MnO 2, is reduced to trivalent manganese hydroxide (its formula can be represented as MnOOH). It gradually covers the oxide grains, penetrates deep into the grains and blocks access to the electrolyte. Even half of the manganese oxide has not been used, and the element has already stopped working; By that time, even more zinc remains, up to four-fifths! In short, an almost usable battery has to be thrown away.

But if you remove the “shell” of MnOOH, the electrolyte will again be able to flow to the grains and the battery will come to life. But how to remove it? The easiest way is to tap the battery firmly with a hammer or stone. Then the grains inside the cells will split, and the electrolyte will again be able to penetrate them. This method is not so good, but in the forest, perhaps, you won’t find a better one...

If the battery fails at home, then manganese dioxide can be activated much more effectively. Punch a hole in the zinc battery cup with a nail and lower the battery into water. The electrolyte in the cell is not liquid (that would be inconvenient), but thickened. It soaks in water, liquefies, and makes it easier for it to penetrate the manganese dioxide grains. This simple trick allows you to increase the battery life by almost a third. But it can be simplified even more.

There is no need to fill the battery with water. All you have to do is punch a hole in the zinc cup. Manganese oxide in the element is mixed with graphite powder - this is necessary in order to increase electrical conductivity. As soon as air begins to flow inside, graphite will absorb oxygen, and along with manganese dioxide, another positive electrode will appear - the so-called air electrode, on which oxygen is reduced. In short, a simple nail transforms a manganese-zinc element into an air-zinc element!

To be fair, let’s say that after such a procedure the battery will be discharged with a low current - such are the properties of a homemade zinc air cell. But it will serve for a very long time.

And the last thing: we will make the old battery almost exactly like a new one. To do this, the battery must be charged with electric current, i.e., treated in the same way as a battery. The reaction taking place in the battery is reversible, and MnOOH can again turn into MnO 2.

Please note that not all batteries can be recharged, but only those in which the paste has not dried out and the case is not damaged. And it is not necessary to charge with ordinary direct current, as batteries are charged. In this case, zinc will begin to deposit on the battery body in the form of branched threads - dendrites, and very soon this will lead to a short circuit and the battery will fail. It must be charged using the so-called asymmetric current. To get it, you need to rectify the alternating current not completely, for example: insert a rectifier diode into the circuit and parallel it with a resistance (about 50 Ohms). The source voltage should be about 12 V, so you cannot use current directly from the network; you need a step-down transformer.

Manganese-zinc cells can be charged up to three times, while their capacity drops very slightly. And small, so-called button cells (they use a mercury-zinc system) can be recharged up to ten times. But there is no point in punching them with a nail or hitting them with a hammer - there are practically no active substances left in these elements after the discharge.

Reviving an old battery does require some sleight of hand. But. You will need it even more if you decide to make a homemade power source. It can be useful for various electrochemical experiments, for example with aluminum anodizing or nickel plating.

There are many chemical current sources, but perhaps the easiest to manufacture is the Grenet element. It requires two plates - zinc and coal of such a size that they fit into a glass jar. Pick up a plastic cover for it, pierce it in two places with an awl and pass wires through the holes. Hang the electrode plates on these wires so that they do not touch each other.

The electrolyte will be an aqueous solution containing 16% sulfuric acid and 12% potassium dichromate (chrompic). When you prepare the solution, pour the acid into the water as always and be very careful.

Carefully pour the electrolyte into the jar; the solution should cover the plates by about three-quarters. Close the jar tightly with the prepared lid with wires and electrodes. The moment the electrodes come into contact with the electrolyte, an electrical potential arises. If a circuit is closed, an electric current will flow through it. This can be easily checked by connecting a voltmeter to the wires: it will show a voltage of about 2 V. However, the current strength is not too high; even a flashlight bulb will not work from the element. But if you make not one, but two or three Grenet elements and connect them in series - a zinc plate with a carbon one, then the light bulb will light. And for an experiment with nickel plating, one Grenet element is enough.

Although the Grenet cell works reliably, it has at least two drawbacks: firstly, it is inconvenient to deal with a liquid electrolyte, which also contains sulfuric acid, and secondly, zinc and carbon plates are not always on hand. Therefore, we will deal with other homemade current sources. Even if they are inferior to liquid elements, there will be no problems with materials.

Tea and cigarettes are often wrapped in foil, one side of which is “silver” and the other is paper. In shops " Young technician» sell copper foil. Cut both into squares of approximately 5 x 5 cm and place one on top of the other alternately so that the copper lies on the “silver”. The bottommost layer should be paper, the topmost layer should be copper. You have a battery of elements; the higher the stack, i.e. the more elements, the higher the voltage.

Cut strips from copper foil - current leads, attach them to the top and bottom of the stack and wrap them with insulating tape, and then immerse the battery in an electrolyte - a solution of table salt. To make sure that the battery has started working, hold a strip of filter paper moistened with a phenolphthalein solution to its poles, as you did before. At the negative pole the solution will turn red. The voltage of such a battery can reach several volts, but the current, unfortunately, is rather weak.

For other current sources, the easiest way would be to use ready-made materials from old, used batteries. Break the batteries and remove from them the active mass of manganese oxide, which coats the electrodes, graphite rods and dried paste (thickened electrolyte) - scrape it off and put in water to swell. Grind manganese oxide into powder and mix with a few drops of photo glue or gelatin solution. Coat a graphite rod or a pencil lead with this mixture, leaving a free area on top for attaching the contact. When the mixture has dried, wrap the rod with “silver” paper in several layers, with the “silver” facing out, and tie it with thread. Wrap one wire tightly around the rod, the other around the “silver” paper and glue it with sticky tape. Wrap the element with insulating tape - it is ready for use.

More advanced elements are obtained if the active mass and paste are moistened with a solution of ammonium chloride (24 g per 100 ml of distilled water; it is useful to add 1 g of calcium chloride). If this solution is heated with starch milk, an electrolyte will be obtained in the form of a paste.

Take a plastic bottle cap, punch a hole in the bottom and pass a wire through it. Place a circle of galvanized iron into the cork; it should be pressed against the down conductor wire. Cut a circle from filter paper along the inner diameter of the cork, soak it in electrolyte, grease it with paste and insert it into the cork. Place the soaked active mass with manganese oxide from an old battery on top and press it with a circle cut from a graphite rod - it will serve as a second current conductor. Such “cork” elements can also be used to create a battery that produces a voltage of several volts.

The plastic stopper can be replaced with an iron one with a tin coating - from a bottle of lemonade or mineral water. Naturally, zinc is no longer needed in this case, just as there is no need to punch a hole in the plug - it itself is electrically conductive, but the tin element produces a low voltage.

An even more advanced element is in the form of a cup made of aluminum foil. The cup can be made using a short (3–4 cm) piece of plastic hose. Inside, place a piece of foil of obviously higher height, press it against the walls, and use the “excess” material to make a bottom and straighten it with a round rod, for example, the back of a ballpoint pen. An aluminum cup will completely replace a zinc one.

Place a cardboard circle on the bottom and lubricate the inside of the glass with thickened electrolyte from an old battery or homemade one. The layer should not exceed 1 mm. Fill a light fabric bag with the moistened MnO 2 mass, seal it by lightly pressing with the same round rod, add the mass to the top and press in the graphite rod (or pencil lead). Lightly compact the mass again, cover the bag if possible and place a second cardboard circle with a hole in the middle on the rod - it will prevent the electrode from tilting. Light a candle and drip paraffin onto this washer, and then onto the bottom of the element for insulation.

Such an element produces a voltage of about 1 V, which is higher than that of an element made from corks. Two or three “cups” make it possible to listen to the transistor receiver through headphones.

So much has been written about growing crystals, and these experiments are so impressive and easy to perform that you have probably done them at least once and know what the principle is. Actually, there is nothing complicated here: you need to prepare a hot saturated solution of some salt (sodium chloride, copper or iron sulfate, alum, potassium bichromate, etc., the list is very long), carefully cool it so that excess dissolved substance does not fall out into the precipitate (such a solution is called supersaturated), and finally introduce a seed - a crystal of the same salt suspended on a thread. After this, all that remains is to cover the vessel with a piece of paper and place it in discreet place and wait until a large crystal grows, which can take weeks or even months; the only thing you have to do occasionally is to add a little saturated solution as it evaporates.

All this is really known. But there are a lot of experimental options, and we will choose not the most common ones, for example, with lead nitrate and potassium iodide. Mix equal volumes of 10% solutions of these salts, and a precipitate of lead iodide will form in the vessel. Carefully drain the liquid from it. Boil water in a transparent vessel, acidify it with vinegar and, while it is boiling, add the still wet precipitate of lead iodide, shaking it. As the liquid cools slowly, golden crystals will grow in it.

A variation on the same theme: pour the solutions of lead nitrate and potassium iodide into a test tube, boil the contents along with the precipitate until it dissolves, and then quickly cool under the tap. In this case, tiny gold crystals are formed suspended in the liquid.

In general, the size of the crystals strongly depends on the cooling rate. Pour 20 g of potassium nitrate in small portions into a vessel with 25 ml of water. After adding the next portion, shake the mixture so that the salt dissolves, and then add the next portion. When the salt stops dissolving, heat the vessel a little, add another portion, shake, and heat again. And so on until all the salt taken has dissolved. Now pour the solution into two vessels, and leave one to cool in the air (for even slower cooling, you can cover it with several layers of thick fabric). Several large crystals are formed in this vessel, and with a successful combination of circumstances, even one crystal. Immediately place another vessel in a pan of cold water, and many small crystals will appear in it. This is a general rule.

The next two experiments are so impressive that they can be safely shown to the audience, of course, having carefully prepared everything. The first of them is the Peligo experience. Wash the inside of a cylinder 25–30 cm high with hot water and pour a hot, very concentrated hyposulfite solution into it through a funnel along the wall so that it fills the cylinder 1/3. This solution is prepared as follows: 450 g of hyposulfite are dissolved in 45 ml of water when heated.

The second solution - sodium acetate (300 g per 45 ml of water) is also poured hot through the same funnel into another 1/3 of the cylinder. Pour very carefully; this solution should not mix with the previously poured solution. Finally, just as carefully fill the upper third of the cylinder with hot water, which will protect the saturated solution from premature crystallization.

There are three layers in the vessel: water, a supersaturated solution of sodium acetate, a supersaturated solution of hyposulfite. Cover the cylinder with glass, let it cool to room temperature, and then you can start the experiment.

Attach a small, inconspicuous crystal of hyposulfite to the end of a glass rod with a piece of wax (melt the wax slightly by heating it over a flame). In front of the audience, quickly lower the stick into the bottom layer. The concentration of salt is so high that many new crystals will immediately pile up around the crystal, forming something like a flower. And in the middle layer, the “foreign” substance around the hyposulfite crystal will not crystallize.

Place another, exactly the same stick with wax, but with a small crystal of sodium acetate (the audience should not notice the difference) into the middle layer - a flower will also grow here, but completely different! The cylinder, if handled carefully, can be used several times.

Another trick-like experience is with sodium acetate alone. Dissolve 100–150 g of salt in hot water (preferably in an enamel bowl) and evaporate slowly, trying to accurately catch the moment when you need to stop evaporation: blow on the surface of the hot solution from time to time, and as soon as a film resembling fat begins to appear, this means that the salt concentration is what is required to form a crystal hydrate of the composition CH 3 COONa * 3H 2 O. Pour the liquid into a clean thin glass, close it and leave to cool. It is enough to add an insignificant amount of seed - sodium acetate - to the cooled liquid so that it instantly crystallizes and turns into a solid mass resembling ice. If you slightly undercooked the liquid on the fire and there was too much water in it, then there will be a little water above the frozen mass that needs to be drained. If there is not enough water, then there will be a coating of salt on the surface. There is no point in removing it; it’s easier to add a little water.

By melting the crystalline hydrate in a water bath and cooling it, the experiment can be done many times, including in front of an astonished public - and who wouldn’t be amazed to see how water freezes before our eyes without cooling? On the contrary, the glass even warms up - this releases the heat of crystallization. The glass can be turned over and not a single drop will spill out of it.

Showing the experience as a trick, try to shake off a grain of salt imperceptibly - say, from the tip " magic wand" And be sure to close the glass tightly between experiments, otherwise even a random speck of dust can cause unplanned crystallization.

The reagent for this experiment, sodium acetate, can be obtained from acetic acid and soda. If you prepare it yourself, then dilute the acetic acid with water about three times and pour soda into it in small portions, gradually, waiting until the foaming from the previous portion of soda stops. Without this, the reaction will proceed so violently that the liquid may be thrown out of the vessel.

And also unusual crystals - metal ones. We will grow copper crystals.

You have already obtained small copper crystals when you dipped a nail into a solution of copper sulfate. They are so small that the copper film on the surface appears almost continuous. And in order to prepare large crystals, it is necessary to somehow slow down the reaction so that the copper released in the reaction has time to settle on the crystals and complete their construction. Slow cooling is a possible method, but in the case when a chemical reaction does not occur...

Table salt will act as a brake on the reaction. Place some copper sulfate crystals at the bottom of a vessel (for example, a glass jar) and cover them with table salt, as fine as possible. Cover them with a circle cut from blotting or filter paper; this circle should touch the walls of the vessel. On top, directly on the paper, place an iron circle of a slightly smaller diameter. Wipe it down in advance sandpaper and rinse.

Pour a saturated solution of table salt into the jar so that it completely covers the iron circle. Everything else will go on without your participation. It is impossible to say exactly how long you will have to wait - much depends on the conditions of the experiment. In any case, not an hour or two, but several days.

So, after a few days you will find beautiful red copper crystals in the vessel. By changing the size of the vessel, the size of the crystals of copper sulfate, the thickness of the layer of table salt and the temperature of the experiment, you can obtain copper crystals of various shapes, sometimes extremely unusual. And sometimes dendrites grow - crystals that are incomplete in development, similar to tree branches.

If you leave copper crystals in the same container in which they were received, they will not last long. Remove them, rinse with water, transfer to a test tube with dilute sulfuric acid and cap. Now nothing will happen to the crystals.

There are substances that are called isomorphic: they crystallize the same way, despite their different composition. Crystals of one such substance are capable of growing in a saturated solution of another: the result is, as it were, a “crystal within a crystal.” If you cut it, there will be a geometric pattern on the cut.

The most accessible among isomorphic substances are alum, crystalline hydrates of double sulfates with the general formula M"M""(SO 4) 2 *12H 2 O. We will use three of their varieties: dark purple chromium potassium KCr(SO 4) 2 *12H 2 O, green iron-ammonium NH 4 Fe(SO 4) 2 * 12H 2 O and colorless aluminum-potassium KAl(SO 4) 2 * 12H 2 O.

Pour water into an enamel or glass bowl, add some alum (one type) and heat, stirring with a glass or wooden stick, but not to a boil. When the salt dissolves, add another portion of the same alum and heat again. When the solution becomes saturated, quickly filter it through a cotton swab placed in a glass or enamel funnel, rinsed with boiling water. If the funnel is cold, premature crystallization may begin and the crystals will clog the funnel.

Cover the jar with the alum solution and leave to cool slowly. Small crystals will fall to the bottom. If they grow together, heat the solution by adding a little water and cool again. Remove the crystals, dry them, transfer them to a test tube and close it with a stopper. Also prepare a crystal of other alum. Save saturated solutions! To avoid mixing them up, put labels on the jars.

Select one crystal of each type, tie it with thin threads (for example, from a nylon stocking) and dip each one into its “own” solution. Keep jars away from drafts; cover them with paper lids.

In about a week the crystals will grow noticeably. Swap them. If you hang two crystals in each jar from the very beginning, there will be even more color alternations. To avoid getting confused, attach tags to the ends of the threads and write down in your laboratory notebook how long the crystals have been in and in what solution.

The correct alum crystal has the shape of an octahedron, but we don't need a perfect crystal. On the contrary, the more bizarre the shape, the more interesting drawing on the cut. At the same time, you can grow crystalline aggregates - druses, using already fused crystals as seeds. If they begin to branch while growing, do not correct them; Moreover, you can control the growth of edges yourself. Lubricate the edge with Vaseline and it will stop growing; wash off the Vaseline with acetone and the edge will grow again.

Cut the finished crystal with a wet, harsh thread; This work requires precision and patience. Level the cut surface with sandpaper and polish it on damp Whatman paper in a circular motion.

Depending on how the cut plane is chosen, how many layers are in the crystal and what their thickness is, you will get a wide variety of geometric patterns. Druze has even more options. Immediately coat the cut crystal with a pattern with colorless varnish (nail polish is suitable), otherwise it will fade and crumble into powder.

It is much easier to make a pattern from crystals of ammonia - ammonium chloride. True, it is colorless, but the pattern reminds us so much... However, let’s not get ahead of ourselves.

Pour ammonium chloride into warm water and mix thoroughly to prepare a saturated solution. Take a glass plate or mirror, wash the surface, and apply the prepared solution to it with a brush. Let the plate with the solution cool slowly in the air, and to prevent dust from falling on it, you can hide it in a closet. After a few hours, the water will evaporate and a pattern will form on the glass. You don’t even have to look closely to understand what it resembles: a frosty pattern on a winter window.

Such an experience, of course, is best put under New Year. Heat does not threaten the artificial frost pattern, but it must be kept away from water...

Searching for treasures is a troublesome and, as a rule, useless task. Still, we invite you to try your luck, guaranteeing complete success. We will look for real gold, and not in a cave or in the forest, but on the most ordinary plate with a gold border. And not even a whole one, but a broken one.

This may surprise you, but the gold rim on the dishes is actually made of gold. Is it true. There is very little of it there, because the layer is very thin. Take a glass with a gold rim and look at the light: the gold layer appears transparent.

Gold is applied to the dishes from a solution. And we will begin this experiment by preparing a solution containing gold.

Stock up on gilded shards - you will receive them for free at the china store. For experiments, approximately 10 cm 2 of gold plating will be enough for you. From it we will prepare about 5 ml of diluted chloroauric acid H. To do this, dissolve gold in a mixture of concentrated acids - 3 ml hydrochloric and 1 ml nitric. This mixture is usually called aqua regia. Concentrated acids must be handled with extreme caution! To work in rubber gloves! Conduct experiments only in the chemistry circle!

Before dissolving, thoroughly wash the gold layer on broken dishes and remove traces of grease by wiping it with a cotton swab soaked in acetone. Take a few drops of aqua regia into a glass pipette and dissolve the gold. Carefully collect the resulting solution of chloroauric acid into a small test tube lined with distilled water. All solutions in this experiment must also be prepared using distilled water and in clean containers.

To use gold more fully, rinse the place where it dissolved with a small amount of water (preferably from a pipette) and collect it in the same test tube. Add water to 5 ml. We will work with this solution. We will prepare a very beautiful cassium purple - a colloidal solution containing tiny particles of metallic gold. It is formed when a solution of tin chloride SnCl 2 is added to a highly dilute solution of chloroauric acid.

Dissolve 0.5 g of tin(II) chloride in 50 ml of water. Pour a few drops of this clear solution into a test tube containing a pale yellow solution of chloroauric acid. At first the mixture will turn yellow-brown, and after a few minutes a wonderful color of cassian purple will appear. In this case, metallic gold is reduced, and the resulting tin hydroxide Sn(OH) 4 imparts stability to the colloidal solution. The color of the liquid is usually intense red, but depending on the particle size it may have various shades- from pink to purple.

Colloidal gold can be precipitated with a solution of table salt. The gold particles combine and sink. After washing and drying, a solution of chloroauric acid can again be obtained from the sediment (using aqua regia).

If you have a hydrogen burner at your disposal, then you can stage a very spectacular experiment - the so-called Donau experiment. A hydrogen flame directed at the surface of a solution of chloroauric acid also reduces gold, and colored stripes appear in the liquid. You can also do this: apply an undiluted acid solution obtained by treating gold with aqua regia onto a clean porcelain plate, dry it, and then place it in the flame of a hydrogen burner. A shiny film of gold forms on the porcelain.

We warn you: the hydrogen torch can only be used with permission and in the presence of the teacher.

In adventure novels telling about ancient times, letters written in colorless ink are sometimes mentioned; cunning enemies do not know the secret of secret writing, and only noble heroes can turn the invisible into the visible...

But there is no special secret here; it has long been known. Some colorless substances seem to appear under the influence of heat, forming colored compounds. Such substances include, for example, lemon juice or onions. Dip your pen in them and write on a piece of paper - nothing is visible. Now hold a piece of paper over a closed electric stove or over a flame, but far enough away so that the paper does not flare up, and the inscription will become clearly visible. The same experiment works well with milk and diluted vinegar.

Several more similar experiments - but not with natural substances, but with chemical reagents. Pour just a little ammonium chloride into a small test tube, on the tip of a knife, and add about a teaspoon of water. Dip the pen into the clear solution, write or draw something on the paper and let it dry. After strong heating, the inscription or design will become clearly visible.

This experiment is even more effective with a highly diluted solution of cobalt chloride CoCl 2. After drying, the lines on a white background are almost invisible, because the crystal hydrate CoCl 2 * 6H 2 O (which is what is formed after drying) is pale pink. But when the leaf is heated, part of the water of crystallization is split off, and the salt turns blue. If you moisten it again by breathing on the paper or, even better, holding it over steam, then the image disappears, because a hexahydrate crystalline hydrate is again formed.

Perhaps you have already encountered this experience. Here is a version of it, much less known. We will not heat the piece of paper with the inscription at all, but to show how you can take away part of the water without heating, we will perform a preliminary experiment.

Pour some concentrated cobalt chloride solution into the test tube. Pink colour. Add an equal amount of acetone and stir: the solution will turn blue! Dilute the solution with water and it will turn pink again.

What happened? Acetone dissolves water well and can take it away from other substances. But if so, then what is written with a solution of cobalt chloride can be developed using acetone and without any heating? Exactly. Wipe the piece of paper with the inscription with a cotton swab soaked in acetone, and the result will be the same as when heated.

Another experience with writing - without a pen and without ink. Flatten a piece of chocolate foil and pin it to the board with thumbtacks. Connect one of the buttons to the negative pole of the battery. Attach a nail cleaned with emery cloth to the positive pole. Moisten a sheet of writing paper with an almost colorless solution of table salt with the addition of red blood salt K3, place it on top of the foil and touch the paper with a nail: a blue mark will appear on it. During electrolysis, Fe 2+ ions, interacting with red blood salt, give Turnboole blue Fe 3 2. It penetrates the paper and attaches itself to its fibers. If instead of blood salt you take potassium thiocyanate KSCN or ammonium thiocyanate NH 4 SCN, you will get not a blue trace, but a red one, because red iron thiocyanate is formed.

Such experiments can be carried out not only with writing paper, but also with scraps of clean white fabric.

Turning the invisible into the visible often provides great help to those who solve crimes. They say that there are always traces at the scene of a crime, but they are not always immediately noticeable. And criminologists look first of all for fingerprints, because for each person they are unique - just as human faces are unique. Of course, experts have subtle methods and suitable substances that make it possible to detect even very weak prints; we will use a rather rough one, but in a simple way.

Prepare a mixture of equal amounts of talc and carbon black (talc is sold in pharmacies, and the preparation of carbon black is described in the chapter on pigments). Breathe on your finger to lightly moisten it and press it onto a clean sheet of paper. The mark on the sheet is invisible, but if you sprinkle it with the prepared mixture, carefully spread it with a soft brush (or just shake the sheet) and pour out the excess mixture, then a clear fingerprint will remain on the paper. There were invisible grease marks on the paper, and particles of the black mixture were adsorbed onto them.

The same experiment can be done with different objects and surfaces - take an old newspaper, cardboard box, plastic or glass tumbler. In the latter case, for better adhesion, you need to take more talc; After the excess mixture is removed from the glass, slightly warm the glass - then the prints on the transparent surface will become more distinct.

Experiments with turning the invisible into the visible, and some other experiments you have done, can be safely shown as tricks. However, tricks produce much more strong impression, if you show them in a row, one after another, surrounding what is happening with mystery, spells and slow passes of the “magic wand”...

We will not reveal the chemical essence of the tricks (and it is not that complicated). Find it yourself, and then you will not only entertain the audience, but also expand your knowledge.

Quantitative relationships must be observed, but not very strictly. To avoid weighing the reagents every time, make measuring spoons out of wood that can hold about 10 mg of dry reagent. You can also use plastic spoons, which are applied to some powdered medicines. Each time we will explain how many of these measurements need to be taken.

First, a trick with turning water into milk. Place five measuring spoons of calcium chloride in one glass, the same amount of sodium carbonate (washing soda) in another and fill with water to about a third of the glass. The solutions will look no different from water. Drain them together and the liquid will turn white, like milk. Without wasting time (otherwise the sediment may sink to the bottom, and everyone will see that this is not milk at all), add a solution of hydrochloric acid in excess to the liquid - and the “milk”, instantly boiling, will again become “water”.

Now the trick is a little more complicated - the water in it will turn not only into milk, but also into ink. For the trick you will need three glasses. Pour two spoons of barium chloride (or strontium) into one, and one spoon of tannin into the other. Pour half a teaspoon of water into both glasses. The powders at the bottom will dissolve after stirring, and there is so little water that from afar the glasses will appear empty to spectators.

In the third glass, place five spoons of double iron and ammonium sulfate FeSO 4 (NH 4) 2 SO 4 (Mohr's salt). Fill this glass with water almost to the top. Everything is ready for focus. In front of the audience, take the third glass, with Mohr's salt, and pour the colorless solution from it into the “empty” glasses. In one of them (where the barium chloride is), the water will instantly turn into “milk”, in the second - into “ink”.

The next trick is no more difficult. Dissolve two spoons of cobalt chloride in a test tube with water (you used it to make invisible inscriptions). Soak a white cotton handkerchief in this solution and dry it. The scarf will turn blue.

The trick is that you show the audience a blue handkerchief, and then crumple it and squeeze it in your hand. If you blow strongly on the scarf several times, it will become moist and turn white again. Unclench your fist and show the white handkerchief to the audience. By the way, it can be used several more times: after drying, the scarf will turn blue again.

For the next trick with color change, you will need three salts: red blood, sodium salicylate and Mohr's salt. You need very little of all these substances, one spoon at a time; dissolve them separately in test tubes half filled with water. The essence of the trick is that red blood salt gives a blue color with Mohr's salt, and sodium salicylate gives a red color. If you lightly outline the outline of a design on paper with a simple pencil, and then moisten it with a brush with two solutions: red blood salt and sodium salicylate - and let it dry, then the audience will not even notice that something has been applied to the paper. Hang a “clean” sheet on the wall and brush over it with a brush dipped in Mohr’s salt solution (tell the audience that this is plain water). The drawing will instantly, right before your eyes, turn red and blue colors.

Another traditional trick is how to light a candle without fire. You probably know the principle of this trick, but a lot depends on its design.

We advise you to do this. Pour the outside of a glass test tube with stearin or paraffin so that it looks like a candle. Close the test tube with a metal cap with a hole through which the wick will pass. Pour some alcohol into the test tube so that it saturates the wick. After this, also fill the cap with stearin or paraffin so that only the wick peeks out. The “candle” is ready.

An ordinary glass rod will serve as a magic wand, on the end of which you will collect a very small mixture of potassium permanganate and sulfuric acid. Warning: prepare the mixture in very small quantities, necessary only for one experiment! Do not touch the mixture with your hands!

You yourself will probably figure out how to arrange this experience (don’t forget about passes and spells). And then touch the wick with a stick - and a flame will immediately flare up at the end of it.

Trick experiments with color changes look very peculiar when they use not just aqueous, but thickened solutions. The thickener can be sodium silicate, an aqueous solution of which is called liquid glass. Office silicate glue diluted twice with water is also quite suitable for magic tricks.

Pour some calcium chloride solution into a glass and add one or two drops of phenolphthalein. Add sodium silicate solution into another glass. As soon as you pour the first solution into it and shake the mixture, it, of course, will turn red, and what is even more curious, thick, like fruit jelly.

Instead of calcium chloride, you can take 3 scoops of magnesium sulfate (pharmacy bitter salt), add water, shake and add a few drops of sodium silicate solution. After stirring, this time a “jelly” is formed, only not bright red, but pale pink.

Colored silicate jellies allow you to “paint” magic pictures. Make a sketch of the drawing, and moisten the areas that need to be painted with a colorless phenolphthalein solution. Moisten another sheet of paper with a solution of sodium silicate - also colorless. Press the sheets against each other and after a few minutes (you can show another trick in the meantime), carefully separate the sheets. The picture “by itself” turned red! For initiates, there is nothing surprising - after all, sodium silicate solutions have an alkaline reaction...

And the last trick, also promised earlier, is with the transformation of “water” into “blood”. Prepare opaque vessel, for example, by covering a glass jar with colored paper; for greater mystery, draw alchemical symbols on paper. Pour water into the jar.

Have a few clean glasses ready. Generally, three is enough, but to give the audience the impression that the transformations are very complex, use five or six glasses. Pour four spoons of potassium hydrogen sulfate into one glass or drop a few drops of acetic acid and mark this glass for yourself (but so that it is not noticeable to the audience) so that it can be immediately distinguished from the rest. Pour a spoonful of soda ash into another glass, and a few drops of phenolphthalein solution into the third. Pour dry reagents with a small amount of water and stir until dissolved. Now you can show focus.

First of all, convince the audience that you are in a bank plain water; and since this is so, you can take a few sips from the can as proof. And then fill all the glasses with water from the jar. Absolutely nothing will happen. Pour all the water back into the jar from all but one of the sodium bisulfate (or acid) glasses. The liquid in the jar will turn red, like blood, and the audience will see this as soon as you pour it back into the glasses.

Drain the contents of the glasses into the jar again - this time from all glasses without exception. The liquid will become discolored, the “blood” will turn into “water”, which you will again pour into glasses. However, you no longer need to drink it.

The experience is simple, but quite effective, if, of course, you don’t forget about the spells...

In experiments that are so similar to magic tricks, colorless solutions were colored first one color or another, and this happened immediately, as if by magic. Indeed, chemical reactions proceed very quickly and, as a rule, begin immediately after mixing the reagents. However, there are exceptions to this rule. The reaction mixture may remain colorless for some time and then immediately become colored. If you want - in five seconds, if you want - in ten; you yourself can set the “chemical clock” for the required time.

Prepare two solutions. Composition of the first: 3.9 g of potassium iodate KJO 3 per liter of water. The composition of the second: 1 g of sodium sulfite Na 2 SO 3, 0.94 g of concentrated sulfuric acid (carefully!) and a little, a few milliliters of starch paste - also per liter of water. Both solutions are colorless and transparent.

Measure out 100 ml of both solutions and quickly, preferably while stirring, add the second to the first. It’s more convenient to do the experiment together - let your friend immediately start counting the time using a stopwatch or a clock With second hand. After six to eight seconds (the exact time depends on the temperature), the liquid will instantly turn dark blue, almost black.

Now measure out again 100 ml of the second solution, and dilute 50 ml of the first with water exactly twice. With a stopwatch in your hands, you will see that the time elapsed from the moment the solutions are drained until they are stained will also double.

Finally, mix 100 ml of the second solution with 25 ml of the first, diluted four times with water, i.e. to the same 100 ml. The "chemical clock" will work four times longer than in the first experiment.

This experiment demonstrates one of the fundamental chemical laws - the law of mass action, according to which the reaction rate is proportional to the concentrations of the reacting substances. But here’s the question: why do the solutions become colored instantly after a pause, and not evenly and gradually, as should be expected?

Sulfuric acid in solution displaces iodate and sulfite ions from their salts. In this case, hydroiodic acid HI is formed in the solution, but it does not live long and immediately interacts with iodic acid HJO 3. As a result, free iodine is released, which gives a color reaction with starch.

If everything went exactly like this, then the solution would darken gradually as iodine was released. However, another process occurs in parallel: sulfurous acid H 2 SO 3 reacts with free iodine and hydroiodic acid is formed again. This reaction goes faster the previous one, and iodine, without having time to color the starch, is again reduced to JO3-.

It turns out that the color should not appear at all? Please note: during the reaction, sulfurous acid is continuously consumed, and as soon as all of it turns into sulfuric acid, nothing will prevent iodine from reacting with starch. And then the solution will instantly color throughout the entire volume.

By diluting the solution by half and four times, you reduced the concentration of potassium iodate, and the reaction rate decreased proportionally.

The explanation seems to have taken longer than the clock experiment itself...

In chemical research, optical methods are very often used. The phenomenon you are about to observe is used to determine the melting point of a substance.

Prepare about fifteen identical plates of thin glass (for example, old photographic plates are suitable). Hot water wash off the emulsion from them and cut them into squares approximately 5 x 5 cm in size. Place ten of these squares one on top of the other and wrap the ends with insulating tape so that the stack does not crumble. Sprinkle some sodium thiosulfate (hyposulfite) onto one of the remaining slices and heat gently until the crystals melt. Heat another free plate and immediately cover the melt with it. A thin transparent layer of molten salt forms between the plates. If it turns out cloudy, add a little, literally one or two drops of water. When the melt cools in air, the hyposulfite will begin to crystallize; this in itself is interesting to observe through a magnifying glass.

Place a sheet of black paper on the table and a clean thin glass on top of it. Turn on a bright lamp and sit at the table so that through the stack you will be holding you can see the reflection of the lamp in the thin glass lying on the table. By changing the inclination of the stack, leaning closer to the table or moving away from it, find a position at which the reflection of the lamp will fade. It is better to look at the stack from an acute angle. If direct light from a lamp bothers you, cover the stack with a screen or palm, but so that you can see the light reflected from the table.

With your free hand, take the hyposulfite strips and place them between the stack and the table so that they are in the path of the light. Turn and tilt them slightly and you will see a very beautiful rainbow.

An explanation of experience would lead us into a world no longer of chemical, but of physical phenomena. We will only tell you how using such stacks - they are called polarizing - the melting temperature is measured. The rainbow you observed only appears in crystals. If you gradually heat a solid substance, then at the very moment when the substance turns into a liquid state, the rainbow will disappear.

During some chemical reactions, some energy is released in the form of light. This process is called chemiluminescence. Sometimes chemiluminescence occurs in living organisms: the most clear example- everyone knows fireflies. A weak glow also appears during the oxidation of some organic compounds. You can observe it in the experiment with the oxidation of hydroquinone. The final stage of this experiment must be carried out in the dark so that the glow is more noticeable.

Dissolve 1 g of hydroquinone and 5 g of potassium carbonate (potash) in 40 ml of pharmaceutical formalin - an aqueous solution of formaldehyde. Pour the reaction mixture into a large flask or at least a liter bottle.

In a small vessel, prepare 15 ml of a concentrated solution of hydrogen peroxide (peroxide). You can use tablets of hydroperite - a compound of hydrogen peroxide with urea (the second component will not interfere with the experiment). Place both vessels in a dark room so that they are within reach. Once your eyes have adjusted to the dark, add the peroxide solution to a large container. Immediately the mixture will begin to foam (which is why we ask you to take a larger container) and a distinct orange glow will appear.

The chemical energy released during the oxidation of hydroquinone with peroxide in an alkaline medium is almost completely converted into light, and not into heat, as usual. However, heat is also released in the reaction, so the formaldehyde evaporates a little. And since it smells unpleasant, then, firstly, do not lean over the vessel and, secondly, ventilate the room immediately after the experiment.

Glow can appear not only during oxidation. Sometimes it occurs during crystallization. This phenomenon has long been known; you can watch it.

The simplest object to observe is table salt. Dissolve it in water, and take enough salt so that undissolved crystals remain at the bottom of the glass. Pour the resulting saturated solution into another glass and, drop by drop, using a pipette, carefully add concentrated hydrochloric acid to this solution. The salt will begin to crystallize and a glow will appear - small sparks will jump through the solution. To notice them, the experiment must also be carried out in the dark.

Some other salts behave similarly during crystallization - potassium chloride, barium chlorate. In all cases, sparks appear only when hydrochloric (hydrochloric) acid is added. But perhaps the most effective experiment is with a mixture of potassium and sodium sulfates. Mix 200 g of potassium and 80 g of sodium salt and add hot water to them in small portions. When all the crystals have dissolved, leave the solution to cool. The room in which you perform the experiment must be darkened. The first, very weak sparks will appear already at 60 °C. Then there will be more and more of them. When a lot of crystals fall out, you will see a whole sheaf sparks, but you have to wait a long time for this - sometimes a whole hour. If you put your ear to the wall of the vessel, you can hear something like thunder. The glow in this case is probably caused by the formation of the double salt 2K 2 SO 4 *Na 2 SO 4 *10H 2 O.

Do not pour out the solution with crystals - the experiment can be repeated after the glow stops. Run a glass rod over the crystals that are under the liquid, or simply shake the vessel with crystals several times - sparks will appear again.

Here is another experiment with glow during crystallization (this phenomenon is called crystalloluminescence). For this, you will have to prepare barium bromate Ba(BrO 3) 2 from more accessible substances - potassium bromate KBrO 3 and barium chloride BaCl 2. Since the solubility of the first of them is low, you will have to take diluted solutions of approximately 3% concentration. If the mixture of reagents is cooled, the desired salt will precipitate: barium bromate is almost insoluble in cold water.

Filter, rinse with cold water and dry the barium bromate, then weigh out 2 g, dissolve in 50 ml of boiling water and filter the solution again. Place the glass with the solution to cool, but not at room temperature, but at a slightly higher temperature - 40–45 °C (best in a drying cabinet). At this temperature, blue sparks will appear in the solution and popping sounds will be heard - again a microthunderstorm in a beaker...

Cool the barium bromate solution prepared in the previous experiment to room temperature; White salt crystals should precipitate. When there are enough of them, rub them with a glass rod. It may not work the first time (it takes skill), but when rubbed, flashes of light will appear.

For what reason - after all, chemical processes no longer take place, and crystallization has also ended?

Indeed, the reason here is different - friction. And this phenomenon is triboluminescence (in Greek tribos - friction). There are substances that are very sensitive to friction and begin to glow in the dark not only when rubbed, but even when shaken. True, these substances are not the most common, but perhaps they are in the school chemistry classroom or in the chemistry club. Here are two of them: zinc sulfide ZnS with the addition of 0.02% manganese sulfide MnS; Cadmium sulfide CdS. However, among the substances that emit light when rubbed, there are also surprisingly ordinary ones. For example, sucrose.

In a large porcelain mortar, place a little refined (i.e., peeled) granulated sugar in the bottom. Enter a dark room and stay there for a few minutes. When your eyes get used to the darkness, first slowly, then gradually increasing the pace, rub the granulated sugar in a circular motion with a porcelain pestle. Soon bluish sparks will appear, which will merge into a luminous ring. If you do not speed up the grinding pace, then sparks will flash under the pestle here and there.

A simplified version of the experiment: firmly hold a piece of refined sugar in your hand and scratch it several times on a rough surface - earthenware, ceramic. Do this as before, in the dark. If your eyes get used to it, you will see luminous stripes that go out as soon as they flare up.

Emission from triboluminescence is explained by electrical discharges arising from the destruction of crystals. That is why it stops when the sugar crystals in the mortar are already ground. Powdered sugar does not glow due to friction.

Now let's prepare some fantastically colored flowers. We will take advantage of the property of some natural dyes to change their color under the influence of the environment - the same property thanks to which we were able to turn plants into homemade indicators.

The English writer Rudyard Kipling has a poem “Blue Roses” - about a girl who rejected a bouquet of red roses, and about a young man who went in search of blue ones, but never found them:

“I have traveled all over the world in vain -
There are no blue roses under the sun."

Just as there are no green peonies, yellow lilies of the valley, or crimson daffodils in the world. And yet you can see them with your own eyes...

In a flask or glass, mix 50 ml of medical ether with the same amount of concentrated ammonia solution - this is the reagent for making a fantastic bouquet. Please remember that ether vapors are highly flammable and should not be on fire nearby. In addition, both liquids have a pungent odor, so the experiment must be carried out in a fume hood or, in extreme cases, in a outdoors.

Place the flower whose color you are going to change over a vessel with a mixture of liquids. Some time later (the exact time will have to be determined in practice for each type of flower) the color will change. Both liquids you use are volatile. Ether vapors extract flower dyes from plant cells, and ammonia vapors create an alkaline environment in the petals. This is why dyes change color, like laboratory indicators.

By treating several different flowers in this way, you will get incredible bouquets. If you're going to surprise unusual flowers your friends, then keep in mind that the bouquet should be prepared shortly before the demonstration, because flowers treated with a mixture of ammonia and ether quickly fade.

It would seem that in an acidic environment, under the influence of some acid vapor, the color of the flowers should be restored. Unfortunately, this is not the case: irreversible processes also occur in flowers, so it is not always possible to restore the previous color.

Sequencing:

Recipe I: 4 g of food grade citric acid, two flints for lighters (contain cerium compounds (III and IV), 12 ml of sulfuric acid solution (1:2), 1.7 g of potassium bromate KBrO 3.

Solution A: Dissolve two lighter flints in sulfuric acid.

Solution B: Dissolve citric acid in 10 ml of hot water and pour potassium bromate into it. To completely dissolve the substances, heat the mixture slightly.

Quickly pour the prepared solutions together and stir with a glass rod.

Observation: A light yellow color appears, which after 20 seconds changes to dark brown, but after 20 seconds it becomes yellow again. At a temperature of 45 degrees, such a change can be observed within 2 minutes. Then the solution becomes cloudy, bubbles of carbon monoxide (IV) begin to appear, and the intervals of alternating color of the solution gradually increase in a strictly defined sequence: each subsequent interval is 10-15 seconds longer than the previous one.

Recipe II: Dissolve 2 g of citric acid in 6 ml of water, add 0.2 g of potassium bromate and 0.7 ml of concentrated H 2 SO 4. Add water to the mixture to a volume of 10 ml, then add 0.04 g of potassium permanganate KMnO 4 and mix thoroughly until the salt is completely dissolved. Observation: There is a periodic change in the color of the solution. The mechanism of chemical reactions can be explained as a redox process in which bromic acid plays the role of an oxidizing agent and citric acid plays the role of a reducing agent:

KBrO 3 + H 2 SO 4 = KHSO 4 + HBrO 3

9HBrO 3 + 2C 6 H 8 O 7 = 9HBrO + 8H 2 O + 12CO 2

9HBrO + C 6 H 8 O 7 = 9HBr + 4H 2 O + 6CO 2

The color of the solution changes under the influence of catalysts - compounds of cerium and manganese, which in turn also change the oxidation state, but up to a certain ion concentration, after which the reverse process occurs.

11.31 Synthesis of pyrophoric iron

Sequencing : prepare pyrophoric iron by combining equimolar solutions of ammonium oxalate and iron (II) sulfate or Mohr's salt. To prepare solutions, you need to dissolve 20 g of Mohr's salt in 20 ml of water, dissolve 7.2 g of ammonium oxalate in 20 ml of water. Pour the solutions together. A precipitate of iron oxalate dihydrate (FeC 2 O 4 * 2H 2 O) will form. Filter the precipitate and thoroughly wash it from ammonium salts. Dry the washed sediment on filter paper and transfer it to a test tube. Place the test tube in a stand at an angle with the hole slightly downwards. Heat carefully in the burner flame; remove any drops of water that stand out with filter paper. When the substance decomposes and turns into black powder, close the test tube. Place the test tube with pyrophoric iron to cool in a safe place away from flammable substances.

Observation: When iron or asbestos is spilled onto a sheet, pyrophoric iron flares up. Spontaneous combustion is explained by very fine grinding and large oxidation surface. Therefore, after the experiment, the remaining iron must be eliminated.

Pyrophoric iron should not be stored as it can cause a fire!

11.32 "Cute" ink

We have to admit that some types of ink have either long since disappeared from use, or are used only for such mysterious purposes as secret correspondence. There are many methods for this type of secret writing, and they all use secret or "sympathetic" ink - colorless or slightly colored liquids. The messages they write become visible only after heating, treatment with special reagents or in ultraviolet or infrared rays. There are many recipes for such ink.

Secret agents of Ivan the Terrible wrote their reports with onion juice. The letters became visible when the paper was heated. Lenin used lemon juice or milk for secret writing. To develop the letter in these cases, it is enough to iron the paper with a hot iron or hold it over the fire for several minutes.

The famous spy Mata Hari also used secret ink. When she was arrested in Paris, a bottle of an aqueous solution of cobalt chloride was found in her hotel room, which became one of the pieces of evidence in exposing her espionage activities. Cobalt chloride can be successfully used for secret writing: letters written with its solution containing 1 g of salt in 25 ml of water are completely invisible and appear, turning blue, when the paper is slightly heated. Secret ink was widely used in Russia by underground revolutionaries. In 1878, Vera Zasulich shot the St. Petersburg mayor Trepov. Zasulich was acquitted by a jury, but the gendarmes tried to arrest her again as she left the courthouse. However, she managed to escape, informing her friends in advance about the plan to escape at the end of the trial, regardless of its decision. A note asking for some clothes contained back side sheet of information written with an aqueous solution of ferric chloride FeCl 3 (Zasulich took this substance as a medicine). Such a note can be read by treating it with a cotton swab moistened with a dilute aqueous solution of potassium thiocyanate: all invisible letters will turn blood red due to the formation of an iron thiocyanate complex.

Members of the secret organization “Black Redistribution” also used invisible ink in their correspondence. But due to the betrayal of one of the Black Peredelites, who knew the secret of deciphering the letters, almost everyone was arrested. Secret letters were written with a diluted aqueous solution of copper sulfate. Text written in such ink appeared if the paper was held over a bottle of ammonia. The letters turn bright blue due to the formation of an ammonia complex of copper.

But the Chinese emperor Qinn Shi Huangdi (249-206 BC), during whose reign the Great Wall of China appeared, used thick rice water for his secret letters, which, after the written hieroglyphs dried, did not leave any visible traces. If such a letter is slightly moistened with a weak alcohol solution of iodine, then blue letters appear. And the emperor used a brown decoction to develop letters seaweed, apparently containing iodine.

Another secret ink recipe involves using a 10% aqueous solution of yellow blood salt. Letters written with this solution disappear when the paper dries. To see the inscription, you need to moisten the paper with a 40% solution of ferric chloride. The bright blue letters that appear during this treatment no longer disappear when dry. The appearance of letters is associated with the formation of a complex compound known as “Turnboole blue.”

Remember the story of the disappearance of Fantômas' note. Vanishing ink can be prepared by mixing 50 ml of alcohol tincture of iodine with a teaspoon of dextrin and filtering the precipitate. Such blue ink completely loses its color after 1-2 days due to iodine volatilization.

Chemical reactions occur very quickly and, as a rule, begin immediately after mixing the reagents. However, there are exceptions to this rule. The reaction mixture may remain colorless for some time and then immediately become colored. If you want, in five seconds, if you want, in ten; you yourself can set the “chemical clock” for the required time.

Prepare two solutions. Composition of the first: 3.9 g of potassium iodate KIO 3 per liter of water. The composition of the second: 1 g of sodium sulfite Na 2 SO 3, 0.94 g of concentrated sulfuric acid (carefully!) and a little, a few milliliters of starch paste - also per liter of water. Both solutions are colorless and transparent.

Measure out 100 ml of both solutions and quickly, preferably while stirring, add the second to the first. It is more convenient to set up the experiment together - let your friend immediately start counting the time using a stopwatch or a clock With second hand. After six to eight seconds (the exact time depends on the temperature), the liquid will instantly turn dark blue, almost black.

Now measure out again 100 ml of the second solution, and dilute 50 ml of the first with water exactly twice. With a stopwatch in your hands, you will see that the time elapsed from the moment the solutions are drained until they are stained will also double.

Finally, mix 100 ml of the second solution with 25 ml of the first, diluted four times with water, i.e. to the same 100 ml. The "chemical clock" will work four times longer than in the first experiment.

This experiment demonstrates one of the fundamental chemical laws - the law of mass action, according to which the reaction rate is proportional to the concentrations of the reacting substances. But here’s the question: why do the solutions become colored instantly after a pause, and not evenly and gradually, as should be expected?

Sulfuric acid in solution displaces iodate and sulfite ions from their salts. In this case, hydriodic acid HI is formed in the solution, but it does not live long and immediately interacts with iodic acid HIO 3. As a result, free iodine is released, which gives a color reaction with starch.

If everything went exactly like this, then the solution would darken gradually as iodine was released. However, another process occurs in parallel: sulfurous acid H 2 SO 3 reacts with free iodine and hydroiodic acid is formed again. This reaction proceeds faster than the previous one, and iodine, without having time to color the starch, is again reduced to IO 3-.

It turns out that the color should not appear at all? Please note: during the reaction, sulfurous acid is continuously consumed, and as soon as all of it turns into sulfuric acid, nothing will prevent iodine from reacting with starch. And then the solution will instantly color throughout the entire volume.

By diluting the solution by half and four times, you reduced the concentration of potassium iodate, and the reaction rate decreased proportionally.

"Combined kindergarten No. 17

"Stream"

Educator

Municipal budgetary preschool educational institution

"Kindergarten No. 9 "Golden Key"

Educator

Research and search activity is the natural state of a child. The fundamental and obvious difference between the research of a child and a scientist lies in the overall result: the scientist discovers new knowledge for all of humanity, and the new that children discover is subjective novelty, only for themselves.

If you have time, show it to me?

They say: the clock is standing.

They say: the clock is rushing.

They say: the clock is ticking,

But they are a little behind.

Mishka and I watched together,

But the clock hangs in place.

V. Orlov.

Once upon a time in kindergarten During a lesson on developing mathematical concepts in children, we discussed what time is. Lisa L. asked the question: “If there is time, how can you see him?”, and Yulia K. asked: “They say that time passes, but why has no one seen his legs?”

From these children’s needs to see and feel the category of time, the idea of ​​​​organizing a research project was born

To begin with, we tried to find out:

As a result, the object, subject and hypothesis of the upcoming study were determined.

Subject of study: devices that allow you to feel the properties of the category of time.

Hypothesis: prove experimentally that if time moves, then it has “legs.”

From here target research work : through acquired and acquired knowledge about time, prove experimentally that time is a category that cannot be seen, but can be felt.

Tasks:

1. Study material on the topic: “Time” (fiction, educational literature, Internet sources);

3. Make models of watches of the future;

4. Make a collage " Time is running, we are changing!”

5. Make a device for conducting an experiment over time;

6. Conduct experiments and experiments to study the properties of time;

7. Defend your research work.

In order to find answers to the questions posed, the children, together with their parents and teachers, took up project activities: read fiction and educational literature; drew models of watches of the future; made collages; initiated the creation of a homemade design of clocks (water, fire), made with their own hands; with the help of their parents, they created a collection of clocks in the group, which included tabletop, wall, wrist, electronic and mechanical watches; carried out various experiments, conducted experiments, checking the assumptions made and answering the questions posed; shared their observations and acquired knowledge with peers and adults.

Learn more about experimentation. It was organized as an active activity for children, involving a mini-defense, in which each child had to be able to explain: what he wanted to know, what assumption he put forward, how he tested the hypothesis put forward, what happened?

Some experiments were initiated by children, but most by us adults. For example, conducting an experiment with an hourglass.

I. Hourglass experiment:“Does time flow?”

Hypothesis: suggested that time is grains of sand that are in hourglass. If they flow (grains of sand) from top to bottom, then we can assume that time is flowing.

Description of the experiment:

They put an hourglass on the table while the children were dressing for a walk and compared, based on the volume of sand in the can, how much time (how many “sand runs”) it took different children to get ready.

They invited the children to sit at the table near the hourglass - 1-minute, 3-minute - wherever they wanted, they were asked to turn the clock over at the same time and for 1 and 3 minutes, respectively, to draw figures using a stencil on paper (as an option: transfer beans from one container to another). The amount of work completed was observed and compared over different time intervals.

After this, we asked the same children to simply sit for 1 and 3 minutes without a task, and concluded that when children are busy doing something, time passes faster.

Conclusion: Along with the grains of sand that flow in the hourglass, time also “flows.” A specific task that children perform is an indicator of measuring a specific period of time. The children were convinced experimentally that time flows.

II. Stopwatch experiment:“Can time jump, run, jump.”

Hypothesis: To assume that time not only flows, but if it has “legs”, then it can jump, run and jump.

Description of the experiment:

They watched how many laps the stopwatch hand would run while the sand was pouring into the hourglass.

They measured everything: how long it takes to run a distance of 30 m, how long it takes to run up to the second floor on foot, how long it takes to overcome the obstacle course on the playground, etc., etc.

Conclusion: Firstly, by observing the second hand with children, it was established that time can not only flow, like in an hourglass, but also jump, gallop, and run. Secondly, we found out that the run of the arrow in a circle (from mark 0) is a minute, and the jump from line to line is a second. Segments of time acquire names.

III. Experiment with photographs:"Time and Photographs".

Hypothesis: To assume that time moves with us does not stand still.

Description of the experiment:

We talked with the children about how a child grows up, what he becomes when he grows up. They offered to bring their childhood photographs (from different periods of childhood).

We looked at the photographs that Lisa L brought.

We looked at illustrations that depict the stages of butterfly development.

Conclusion: The children in the first and second examples noted that all living things develop and grow, and time passes with them.

IV. Experiment with the “birthday” circle guide:"Time and Events".

Hypothesis: assume that time flows along with important events from the life of a child.

Description of the experiment:

To trace the passage of time over a period of 1 year, together with the children we decided to make a “birthday” circle (which is divided into four colored sectors according to the seasons). The children glued photographs of the birthday people to each sector.

Using this circle, we decided to track the year not only by the dates of birth of children, but also by holidays celebrated in kindergarten. The children also distributed photographs of festive events into sectors of the circle.

Conclusion: Based on the results of the experiment, we came to the conclusion that time passes through the events occurring in the life of a child.

We conducted an interesting experiment using a homemade water clock design.

The children suggested taking a cut-off bottle, filling it with water, closing it with a lid with a small hole, and placing it in another empty bottle, bottom up. We sit, watch, note how many circles the second hand will run while the water pours into the bottle. Afterwards, we made measurements on the bottle (one measurement = 1 minute, or if you use a stopwatch, then one “run” of the hand around the circle of the stopwatch). Here is a water clock of your own design.

After another conversation with the children about antique fire watches, they suggested making them with their own hands. We attached metal balls to the sides of the candle, which fell as the wax burned out and melted, and their impact on the cup was a kind of sound signal of time.

Children on by example We were convinced that it is impossible to determine the exact time using these watches, and they are not convenient to use at the present time.

Results

During the study, the guys came to the conclusion that time is an abstract concept, it cannot be touched or seen, we can only realize it, feel it through the length of actions. For a child, time is always connected with something, with some kind of pastime, an event that is happening to him, remains in his past or is planned to happen in the future.

Bibliography:

1. Nepomnyashchaya general abilities. - Childhood - Press, 20 p.

2. Richterman's instructions about time in children preschool age. - M.: Education, 19 p.

3. Shcherbakova teaching mathematics in kindergarten. - M.: Academy, 20p.

For a long time I was too lazy to write some kind of drawing lesson. Now is the time to pamper the readers at the same time a funny story about drawing. In the previous lesson I tried . Today I'll try. So let's get down to business. First we take everything necessary tools for this task (pencil, paper and eraser - this is quite enough). Step one: we carefully look at how it should work out and try to remember.

Step two: Draw a large ellipse - . On the left side there are two small circles, which will later become eyes. And on the right there are two more ellipses, this is the future tail. We can see what we should get in the picture: Let's move on. Our fish must swim well, so we will attach fins to it on top and bottom. So that the picture turns out to be cheerful and not gloomy =) A-a-a! And, of course, to make the picture more believable, we also draw bubbles: You can already see the appearance of our future fish quite well. Along the way, we'll work a little with the eraser to remove the extra lines. we draw patterns. And on the body we draw several wavy lines that will represent scales. Soooo! Let's look carefully at the work done. It turned out well, only a small matter remains. Let's make the necessary lines thicker, and work on the rest with an eraser. And at the end the drawing should look like this: Look at it carefully, and now look at what you have =) We laughed together) And here how I drew a fish.

Nice little fish!

Write in the comments what you think about this lesson and more. Let's learn to draw together =) And don't forget to watch the following lessons.